Method for manufacture and use of the waste stream from biodiesel production (crude glycerin) as a commercial fuel

ABSTRACT

The biodiesel manufacturing process generates between 10% and 20% crude glycerin as a waste stream. Due to the rapid rise in the production of biodiesel, this waste has become a significant burden to the industry. This patent establishes a method to transform the crude glycerin into a useful fuel in some applications where waste petroleum oil or heavy fuel oil is currently used. A side benefit of this process is that the biodiesel manufacturer can use this fuel as a secondary profit stream.

FIELD OF THE INVENTION

This invention relates to the processing and use of the waste stream ofbiodiesel production as a commercial fuel. The invention relates to theprocessing of this waste stream to prepare it for optimal combustion andits use in a modified fuel burning system.

BACKGROUND OF THE INVENTION

Due to the rapid expansion of the biodiesel industry, its waste product(crude glycerin) has become a significant disposal issue. This inventionsolves this problem by allowing the glycerin to be processed into auseful fuel. Since it is renewable and made from vegetable or animaloils, it has a very low sulfur content, very low ash content and arelatively high BTU content of approximately 124,000 BTUs per gallon. Ithas some significant benefits over petroleum and coal as an industrialenergy source. It has a sufficiently high flashpoint to make it stableenough for relatively safe use either as a process fuel either in thebiodiesel manufacturing industry itself or as an industrial boiler fuel.By burning crude glycerin, tens of millions of gallons of fuel can beadded to the supply chain annually.

SUMMARY OF THE INVENTION

To successfully produce and use this fuel, five parameters must be met.First, the glycerin must be properly filtered to remove particles thatcould interfere with the passages in the burner equipment. Second, anaccelerant (typically the alcohol used in the biodiesel manufacturingprocess itself) must be added (or maintained if methanol is notrecovered in the biodiesel process) in a proportion that improvescombustion, but maintains safety. Third, the fuel must be raised to atemperature close to its native flashpoint (145 degrees F. in the caseof methanol) to improve combustion. Fourth, all applicable governmentalregulations must be met. Fifth, some equipment modifications may need tobe made to protect equipment from its inherent high ph level.

Previous attempts to use crude glycerin as a fuel have not included anyof the above parameters, nor has reliable combustion been accomplishedin a publicly documented commercial operation.

DETAILED DESCRIPTION OF THE INVENTION

Crude glycerin has different characteristics than a typical fuel oil andthey must be accounted for to obtain proper combustion. First, it has asignificant amount of “sludge” left over from the biodieselmanufacturing process. Second, it has a high flashpoint and relativelyhigh viscosity even at recommended temperatures. Third, it has high“base” properties. Fourth, it does not mix and suspend well withpetroleum products. The following will outline how these characteristicsare modified to allow a more reliable combustion.

It is necessary that the crude glycerin be properly prepared for thecombustion cycle. The piping that is used to drain the glycerin from(the reaction vessel or system and move it to a holding tank prior tothe burner) must have a filter system. This system is made up of twofilters with pressure gauges to allow an indication of when the filtersneed to be cleaned. A manifold with shut-off valves is built around thefilters so that either one can be isolated for safe filter cleaningwhile the other allows continued operation. To improve durability, thefilters need to be wire mesh with a rating that is finer than thesmallest passage or port within the burner to keep internal parts fromplugging. This is most likely to be the port in the burner nozzleitself. The filter seals need to be replaced with seals that arespecifically manufactured for the particular alcohol that is being used.Prior to the filter system, a temperature reduction system needs to beinstalled if the alcohol exits the reactor above its boiling point. Thisallows the filters to be cleaned while the alcohol is in a liquid(safer) state. Since provision is made for a filter separate of theburner, it is recommended that the burner filter itself be removed.

Depending on the exact alcohol content of the glycerin, which alcohol isused and the temperature of the glycerin as it enters the burner; morealcohol may be required to improve combustion. This can be done byadding a venturi along with a passive mixing pump of the kind thatswirls the two liquids as it is being moved through the piping towardsthe storage holding tank. Provision within this area must be made formixing the fuel on an “as needed” basis, particularly if the system isshut down for more than about 12 hours. Typically at least 20% methanolcontent is required for sustainable burns.

Immediately prior to entering the burner, both the processed crudeglycerin and the combustion air need to be brought up to a temperaturejust below the boiling point of the alcohol (145 degrees F. in the caseof methanol). This is necessary to bring the fuel as close to its flashpoint and possible and to improve fuel atomization. This should not bedone before the burner's final fuel filter as the pressure drop acrossthe filter can vaporize the fuel (mainly the alcohol) enough to causethe burner's fuel pump to cavitate.

As in the case of any type of fuel, proper storage and handling of thecrude glycerin needs to be addressed. It will have a flash point ofaround 60 degrees F. due to the methanol content. Vapors from themethanol can present a health hazard to humans if exposure is aboverecommended OSHA levels. All fire code regulations need to be met.Should the fuel be transported, all applicable regulations need to bemet. All insurance requirements will need to be met. Should the fuelneed to be stored for lengthily periods, its high ph may need to becompensated for. This can either be done chemically or by the additionof a more acidic carrier fuel—like vegetable oil.

Some modifications will need to be made to the burner and relatedequipment. In general, the fuel pressure will need to be raised alongwith higher-pressure combustion air. This improves atomization andtherefore provides an improved burn with lower emissions. Provisionneeds to be made for assisting ignition under a cold chamber condition(upon start-up). This can be done with either a torch through a port ora constantly operating pilot light. Once the chamber reaches operatingtemperature, ignition should be self-sustaining. If there are any sealswithin the burner system that will be exposed to the fuel, they willneed to be replaced with a material that is compatible with alcohol(likely methanol) and a high ph (as high as 11.5).

Flame temperature can be adjusted through either increasing the fuelpressure or air pressure or combustion air availability. Flametemperature needs to be maintained above 1800 degrees F. to promoteproper combustion and minimize pollutants.

While specific embodiments of this invention have been described, itwould be obvious to those skilled in the art that various other changesand modifications can be made without departing from the spirit andscope of the invention. It is therefore intended to cover in theappended claims all such changes and modifications that are within thescope of this invention.

1. Applies to the manufacture and use of the waste product frombiodiesel production, commonly known in the trade as “crude glycerin”,as a fuel. Other, less frequently terms used are glycerol, glycerides,fatty acids.
 2. Applies when the crude glycerin is used “as-is”, or ifan accelerant is added to promote combustion by lowering the flashpoint.The accelerant is most likely to be the alcohol used in the biodieselmanufacturing process, which would be methanol or ethanol. Also appliesif the crude glycerin is used either as a primary or secondary fuel. 3.Applies when the crude glycerin, accelerant or primary fuels arerequired to be mixed to provide a uniform fuel mixture.
 4. Applies whenthe fuel (either 100% crude glycerin or a mixture of glycerin andalcohol) is filtered to keep parts within the burner from plugging. 5.Applies if it is necessary to replace metal or elastomeric parts withinthe burner and storage/fuel delivery system to allow improved durabilityof the burner system.
 6. Applies when the crude glycerin is burned ineither a commercially available burner system or in a specially designedand modified system. The “specially designed and modified system” wouldinclude either a method to raise the temperature of the fuel and/orcombustion or atomizing air to bring the fuel closer to its flashpoint.Preheating may also be required to lower the viscosity of the fuel topromote proper atomization to improve combustion.
 7. Applies if or whenan acid is added to the fuel to neutralize the ph of the fuel to protectstorage, delivery or burner parts.
 8. Applies when the crude glycerin iseither burned at the place of the biodiesel manufacturer or if it isshipped off-site.
 9. Applies when any legal or governmental provisionsor regulations are required to be met in order for the crude glycerin tobe used or classified as a “fuel”. This includes, but is not limited totaxation, identification (dying), storage, environmental ortransportation restrictions.
 10. Applies to the waste stream from thebiodiesel process regardless of the raw material used (fresh or wastevegetable oil or animal fat).
 11. Applies when any fuel related testingis required, such as BTU content, sulfur content, ash content or relatedtesting by any end user or governmental entity prior to the use of thecrude glycerin as a fuel.
 12. Applies when any consulting or technicalservices are required for determination of applicability of equipment,training or determination of parameters required to burn the crudeglycerin.